In an electrophotographic image forming apparatus, a process unit forms an electrostatic latent image corresponding to an image to be printed, and makes the electrostatic latent image visible. Specifically, the process unit includes a photoreceptor and a developing device, and forms an electrostatic latent image on the photoreceptor and develops the electrostatic latent image (makes the electrostatic latent image visible) with use of a toner supplied from the developing device. A toner image formed on a surface of the photoreceptor by development is transferred onto, for example, a transfer belt, and the toner image is transferred from the transfer belt onto paper, and thereafter fixed onto the paper by a fixing device.
Furthermore, in the image forming apparatus, in a case where a toner in the developing device is consumed by development, a toner is appropriately supplied from a toner cartridge to the developing device. The toner cartridge is replaced with new one when no toner remains in the toner cartridge. Similarly, the process unit is replaced with new one when, for example, a predetermined number of sheets of paper have been printed.
Image forming apparatuses used in small offices and home offices have been downsized and designed to occupy a smaller space. On the other hand, in small offices and home offices, document files, books, bookshelves, cabinets, etc. are provided on sides of the image forming apparatuses in many cases. This makes it difficult to secure spaces on the sides of the image forming apparatuses. For this reason, such an image forming apparatus is mainly configured such that a worker can replace a toner cartridge, a process unit, etc. at a position in front of the image forming apparatus.
In a case where an image forming apparatus is configured such that a worker handles a toner cartridge while opening a front door of the image forming apparatus, it is necessary to provide a working space for the worker in front of the image forming apparatus. However, in small offices and home offices, there are many cases where a sufficient working space cannot be secured even in front of an image forming apparatus. Examples of such cases include a case where a worker's movement in forward and backward directions in front of the image forming apparatus blocks other person's passage. This is likely to make a smooth working operation difficult.
One possible solution to this problem is to provide a side surface of the image forming apparatus with a door for a working operation, so that a worker can handle a toner cartridge etc. at a position in front of the image forming apparatus.
For example, Patent Literature 1 describes an image forming apparatus having, on a side surface thereof, an openable cover which opens backward. A cartridge holder is provided at an inner surface of the openable cover. A toner cartridge can be inserted into and drawn out from the cartridge holder in obliquely forward and backward directions. Furthermore, a toner cartridge can be attached to a predetermined position of the image forming apparatus by closing the openable cover.
Patent Literature 2 describes an image forming apparatus having, at a side surface thereof, a side cover which opens downward and which has a cartridge storage section. A toner cartridge can be inserted into and drawn out from the cartridge storage section in obliquely upward and downward directions while the side cover is open. Furthermore, a toner cartridge can be attached to a predetermined position of the image forming apparatus by closing the side cover.
In response to a demand from a market, electrophotographic apparatuses of a color output type have come to occupy a larger part of whole electrophotographic apparatuses. In particular, recently, since a processing speed for a color output has been required to be as high as that for a monochrome output, color image forming apparatuses of a tandem type including photoreceptors and developing devices for respective colors have become dominant. In such a color image forming apparatus, monochrome toner images are formed on respective photoreceptors, and these monochrome toner images are sequentially superimposed so as to form a color image on paper. There are two types of a color image forming apparatus of a tandem type: one which sequentially superimposes four color toner images directly on paper so as to transfer the color toner images; and one which temporarily and sequentially superimposes four color toner images on an intermediate transfer member and then transfers a resulting image on paper.
On the other hand, with advance of technology, large multi-color image forming apparatuses are tend to be avoided, and image forming apparatuses so downsized as to be provided on a desktop PC rack etc. are coming into practical use. However, such downsizing of an image forming apparatus complicates a structure within the apparatus. This easily causes difficulty in a maintenance operation.
In consideration of downsizing of an image forming apparatus and workability in a replacement operation of image forming units, it is advantageous to integrate a plurality of image forming units. For this reason, a configuration often employed is such that in each of a plurality of (four or three) image forming sections provided inside an image forming apparatus, a photoreceptor drum, a cleaning unit, a charger, a developer, etc. are integrated so that each of the plurality of image forming sections becomes an image forming unit which is detachable from the image forming apparatus.
Such an image forming apparatus is promoted to be downsized and to occupy a smaller space in order to be usable in a SOHO (small office, home office) environment. However, in the SOHO environment, it is particularly difficult to secure a space on a side of the image forming apparatus. For this reason, a dominant type of the image forming apparatus is one in which a worker can exchange a toner cartridge, a process unit, etc. from a position in front of the image forming apparatus.
In the image forming apparatus described in Patent Literature 2, a toner cartridge is attached/detached for replacement thereof while a side cover supported by a hinge at a lower part of the side cover is opened. Furthermore, a process unit is attached or detached while a front cover supported by a hinge at a lower part thereof is opened. A paper feeding tray is attached to/detached from a tray-containing section by sliding the paper feeding tray in forward and backward directions from a front of the apparatus.
In the image forming apparatus described in Patent Literature 1, while an openable cover supported by a longitudinal hinge at a right side wall of the image forming apparatus is opened in a backward direction of the image forming apparatus, an image forming unit integrated as a replacement unit is attached/detached and a toner cartridge is attached/detached to/from the image forming unit accompanied by replacement of a toner cartridge. Although a paper tray is described as a part of a paper feeding device, Patent Literature 1 does not clearly describe a direction in which the above attachment/detachment is carried out.
In an image forming apparatus described in Patent Literature 3, an image forming unit and an intermediate transfer member are integrally formed as an indirect transfer unit, and the indirect transfer unit is detachable from the image forming apparatus. Patent Literature 3 does not clearly describe how a cover, door, etc. which open when the indirect transfer unit is attached/detached are supported and in what directions the cover, door, etc. open. Further, Patent Literature 3 does not clearly describe in what direction a paper feeding tray is attached/detached.